Automatic balance tab



P 1944- H. P. FOCHT AUTOMATIC BALANCE TAB 2 Sheets-Sheet 1 Filed Aug. 23, 1940 FIG. 2.

INVENTOR HAnm' P FocHT.

ATTORNEY Sept. 5, 1944 H. P. Focl-rr AUTOMA'I IC BALANCE TAB Fil ed Aug. 28, 1940 2 Sheets-Sheet 2 ATTORNEY They are further arranged as his!!! 'for'a trimtab .on which it is mounted,

Patented Sept. 5, 1944 auroua'rro m;

.m r. l'oclit, Km, N. Y., assignor to our- 7 use-Wright Corporation, a corporation of Delaware Application 1mm zt, 1a4o. Serial No. 354,540 a Claims. (01. 244-112) This invention relates to control devices ior provides means for aircraft and in particular automatically differentially controlling a trailing edge tab or flap with respect to a movable control surface upon which the tab is mounted.

In the prior art there are showings of auxiliary.

tabls or naps controllably disposed at the rear edges of control airfoils such as rudders, elevators, or ailerons. Such-tabs may be moved with respect to 'the control airfoils either by setting or by setting them through an aircraft pilot. servo devices to assist in the control of the airfoil but, so faras applicant is aware, none have been provided with mechanism whereby the angle of incidence of the tab may be changed in the same or opposite sense as the control airfoil as the latter is moved,

them on the-ground, control devices operable by and in a different angular degree from the control airfoil movement. Accordingly; it is an ob- Ject of this by which the tab may be moved differentially in either the same direction First referring to Figs. 1, 2, and 3, I show a member II which may comprise a wing, fin, or horizontal stabilizer which is fixed with respect to an aircraft. To the trailing edge of the member pin II, a control airfoil I2 is [0, upon a hinge mounted in any convenient manner. As shown,

the member ill carries a bracket l3 provided-with a yoke H the rear ends of which carry the hinge H.. The air foil l2 comprises a transverse beam I! having projections i6 engagingthe hinge H. To the trailing edge of the airfoil and disposed rearwardly' of the hinge the ends of which are connected by cables or control rods l9 and clevised at their rearward ends, as at 2| and 22, tov the tab 23 at pivot points disposed above and below forward extension 24 is rigid with the rock arm it, this member having a pivot 25 disposed for- Y ward of the airfoil hinge II, this pivot being invention to provide control mechaor in the opposite direction fromcontrol airfoil movement. 5 It is a further 0 vide means by which trim tab may differential movement features are still operative upon control airfoil movement.

' A further object of the invention'is to provide ject of this invention to, prothe neutral setting of the tab control means whereby the angular relationship of the tab with respect to the control airfoil airfoil is moved.

A further object is to provide means for moving the tab to a lesser angular extent than the angular movement of the controlled airfoil, and still another object is to provide mechanism for moving a trim tab to agreater angular extent than I the movement of the control airfoil on which his mounted.

Further objects of the invention will become apparent in reading the description below'in connection with the drawings, in 'which:

Fig. 1 is a longitudinal section on the line of Fig. 2, a fixed airfoil, a movable control airfoil. and a trim tab serially arranged;

Fig. 2 is a fragmentary plan of the assembly of Fig. 3 is an enlarged view of a portion of Fig. 1: and f Fig. I is a view showing an alternate arrangement of the invention.

changes as the control be controllably changed while the similar in aspect to Fig. 1 but therewith but, since said pivot and disposed on opposite sides of the hinge axis ll, 'will be tangled with respect to desired degree of secured to a strut 28 adjustable in length by a I screw shift or the like, the strut being secured to the aircraft and being changeable in length leading to the control through a control cable 21 e controlairfoil {2 1s cockpit of the aircraft. provided with a horn As the control airfoil I2 is moved about its hinge axis II, the pivot for rock arm l8 moves pivot 25 are the rock and itself the control airfoil l2 and with respect to the fixed member Ill of the aircraft. The actual angular movementof the rock arm l8 will be less than that of the airfoil l2. Since the rock arm is controllably connected to' the trim tab 23, the latter will move both with and with respect to the airfoil l2 and, depending upon the spacing between the rock arm pivot, the axis II, and the pivot 25, will have an angular movement intermediate the neutral plane and the plane of the control airfoil l2. This is readily seen in Fig. 1 wherein, when the airfoil I2 is raised, the'tab 23 is raised there'- with but its angular movement is less of the airfoil but still it makes a definite angle with respect to the neutral plane. By adjusting the positions of the above mentioned pivots, a

affecting the control forces which the airfoil l2 produces upon the aircraft when it is displaced.

To afford a trimming control in the neutral position, the strut length 28 may be varied through the cable 21 by which the trim tab 23 is llisarockarmlif the tab hinge H. A'

28 which is connected to the control system by conventional means, not shown.

than that diiferential movement may 'be secured to allow the trim tab to act as a servo-- control for the control airfoil l2 without'adversely moved with respect to the airfoil l2; the angular displacement afforded by this trimming will remain in effect when the control airfoil I2 is displaced from its neutral position.

In Fig. 4 the control elements If! and 20' have been crossed so that movement of the tab 23 in an angular sense is greater than movement of the control airfoil I2 when the latter is controllably moved by' the pilot. In this arrangement, the trim tab 23 will serve for trimming as previously described, but will augment rather'than diminish the control forces afforded by the control airfoil l2. In the arrangement of Fig. 4, the tab 23 does not act as a servo tab but, since its angular displace nt' will be greater than that of the control airfoil, s mewhat greater effort will be needed to move the control airfoil than would be the case if the trim tab were fixed in its angular relationship with respect to the control airfoil.

The arrangement herein disclosed affords a means for varying the effectiveness of -the air control in an aircraft without major changes in.

modifications may bemade therein without departing from the spiritor scope thereof. I aim in the appended claims to cover all such modifica-,

tions and changes.

I claim as my invention:

1. In aircraft comprising a control airfoil hinged near its leading edge to the aircraft for controlled movement, a tab hinged substantially at the airfoil trailing edge, a bellcrank hinged in the airfoil at a point rearward of the airfoil hinge, means connecting one arm of the bellcrank with the tab, the other arm of the bellcrank extending forwardly of the airfoil hinge, and pivot means to adiustably fix the forward end of said other arm with respect to the aircraft.

2. In aircraft comprising a control airfoil hinged near its leading edge to the aircraft for controlled movement, a tab hinged substantially at the airfoil trailing edge, a support rigid with the aircraft, an arm adjustably and pivotally secured at its forward end, forward of the airfoil hinge, to said support, said arm extending rearwardly past the airfoil hinge, a pivot mounting for the rear end of said arm on the airfoil at a location rearwardly of the airfoil hinge, and means for connecting the tab to the arm for transmitting arm movements to the tab.

HARRY P. FOCHT. 

